It is well known to mount accessory equipment to standard rifles in order to add capabilities to suit particular circumstances or mission requirements. For example, Kurak U.S. Pat. No. 4,733,489 shows a way in which a grenade launcher can be conveniently secured to the barrel of an automatic rifle. It is also known to secure a rail of standard design to the barrel of the rifle which in turn will accept accessories, such as lights, lasers, sights, grenade and flare launchers, that are adapted to be secured to the rail of standard design. See E'Nama U.S. Pat. No. 5,198,600. One such rail of standard design is the “Picatinny rail”, apparently so-called because it was developed at the U. S. Army's Picatinny Arsenal. See Oz U.S. Pat. No. 6,854,206, which teaches attachment of a Picatinny or “Weaver” rail to the front sight of any of a family of automatic rifles.
Ser. No. 61/071,590 provided a further improvement over the art discussed above by provision of a mounting structure comprising at least two mounting rings each made up of mating ring halves, to be attached to an existing grenade launcher already having been mounted on a rifle. The mounting structure of the invention then accepts one or more Picatinny-type or other standard mounting rails, which in turn can accept any of a variety of accessories, such as gripping handles, laser or infrared sights, flashlights, and the like.
One standard grenade launcher used by the US armed forces, the so-called M203, comprises a receiver, a barrel assembly, and a trigger assembly. The trigger assembly is fixed to the receiver, while the barrel assembly slides forward to allow ejection of a spent round and insertion of a fresh round. In order to allow the barrel assembly to slide forward, it is necessary for the soldier to operate a catch fixed to the receiver. This requires the soldier to hold the weapon in one hand and operate the catch with the other, which is awkward. It would be preferable to provide a mechanism which would allow the soldier to release the barrel of the grenade launcher and slide it forward without moving either hand from its normal firing positions.